458 KINSHIP AND ADAPTATION 



a single plant. These three forms were found to come true 

 to seed and when crossed the seedlings were like one parent 

 or the other; or occasionally other new forms were produced, 

 with or without crossing, which were as unlike the parent 

 form as were the two new forms first discovered. In the 

 course of seven generations several such new forms appeared, 

 numbering in individuals about eight hundred out of a total 

 of about fifty thousand plants raised. Similar forms also 

 appeared in the field. All these new forms were distinct 

 types differing from one another in several particulars such 

 as shape and color of le;ives, flowers or fruit, and annual, 

 biennial, or perennial ha))it; and although growing together 

 they did not intergradc. They were thus as sharply definable 

 as species are, and they could be regarded as true species 

 except for the fact that their differences distinguished parent 

 from offspring. De Vries regarded them as elementary species 

 equivalent to what botanists have been calling well-marked 

 varieties, races, or subspecies, and as representing the abrupt 

 changes through the accumulation of which species and higher 

 groups arise. He calls variations of this sort mutations/ the 

 new forms l)cing termed mutants. Hence we may designate 

 as mutationism this new theory of evolutionar}^ change. 



Mutationism supposes that from time to time, especially 

 under the influence of changed conditions, some of the in- 

 dividuals of a species bear ofl'spring distinctly different from 

 the parent, often in several particulars, and that the set of 

 peculiarities thus suddenly arising is completely hereditary 

 even when individuals of the new form are crossed with 

 otlier forms of the same species. That is to say, the progeny 

 from parents of two different mutations are like one or the 

 other ]iarent, anil n(!ver intermediate as is often the case with 

 crosses between fluctuating variations. If mutations again 

 mutate and we have mutants of the second or higher degree, 

 their hybrids may l)e wholly like one parent or the other, or 

 may be apparently intermediate from having inherited one 

 or more peculiarities from one ]iai-ent and the rest from the 

 other; but such cases of a,])i)arently intermediate forms show 

 new combinations of eli'ments rather than el(>ments of an 

 ' Mu-ta'lion < !>. niiiliitio, a changing. 



